Derivatives of benzene and biphenyl have been used as liquid crystals and these U.S. Pat. Nos. such as 4,130,502; 4,330,426 and 4,331,552 illustrate these types of the benzene and biphenyl derivatives. These liquid crystals have, relatively speaking, high viscosities. Another U.S. Pat. No. 4,406,814 uses an ester of cyclohexanoic acid as liquid crystals to get lower viscosities but these viscosities are still higher than desired in many cases. Also, the ester group is susceptible to hydrolysis so they have a degree of instability.
Thus, the patents mentioned above are characterized in one aspect as having essentially 4,4' substitution in the cyclic rings such as benzene, biphenyl or cyclohexane whereas U.S. 4,406,814 is the exception as it teaches the use of substituents in the other position of the cyclohexane ring.